X-ray tube



Oct. 12, 1954 w. H. BOLDINGH 2,691,735

X-RAY TUBE Filed June 6, 1952 in 1 3 2' x9 5 L a I i i 1 BY E PatentedOct. 12, 1954 X-RAY TUBE Willem Hondius Boldingh, Eindhoven.Netherlands, assignor to Hartford National Bank and Trust Company,Hartford, Conn., as trustee Application June 6, 1952, Serial No. 292,032

Claims priority, application Netherlands June 15, 1951 3 Claims. (01.250-65) In medical examinations with X-rays, more particularly of thestomach and intestine canals, it is known to determine with the use ofan X-ray screen the favourable area and the useful moment for taking anX-ray photograph. It is then possible to proceed in different ways. Useis preferably made of an X-ray tube comprising two filaments, one ofwhich is switched-in during screening and other when photographic imagesare taken. The filaments are so proportioned that one of them produces asmall focal spot on the anode which is used for screening and whichprovides an image of high definition on the X-ray screen, whereas theother cathode produces a larger focal spot, so that the tube is loadedmore heavily in taking photographs.

After the investigation with the use of the X-ray screen has beenterminated, the high tension is switched off and the heating currentswitched-over from the cathode for screening to the cathode forphotographing. Subsequently, the screen is replaced by the X-ray filmcassette. Upon again switching on the high tension for takingphotographs, the filament intended therefor requires to be heated up tothe required temperature. The time required for heating up saidfilament, that is the time in which the temperature increases to that atwhich the required electron emission takes place, causes the moment ofphotographing to be delayed,

The object of the present invention is to limit this delay as much aspossible. The invention relates to circuits for incandescent-cathodeX-ray tubes comprising two filaments connected to a source of supply,for example the secondary winding of a heating-current transformer, andfurthermore to X-ray devices comprising such circuits.

According to a feature of the circuit according to the invention, thetwo filaments are connected to the source of supply by means of a commoncurrent conductor, the second supply wire for one filament including aswitching arm for closing and interrupting the circuit which, in theopen position, short-circuits a resistance in-. cluded in the secondsupply wire for the other filament. By suitable proportioning of thesaid resistance it is ensured that, during the screening process, whenthe filaments are both connected to the source of supply, theincandescence temperature of the cathode for photographing acquires avalue at which any appreciable electron emission just does not takeplace. The current flowing through the said cathode is then too smallfor producing active X-rays, but the time required to heat the filamentto the emission temperature for obtaining sufiicient radiation isconsiderably reduced.

The invention will now be described in greater detail with reference tothe circuit-arrangements shown by way of example in Fig. l and Fig. 2 ofthe accompanying drawings.

Fig. 1 shows an X-ray tube 1, of which the cathode 2 and the anode 3 arearranged with suitable spacing within a glass vessel 4. The cathode isconstituted by a focussing device 5 having a cup-shaped cavity 6. Thisshape is advantageous for focussing the electrons emitted by thefilaments 'l and 8, when travelling to the anode under the action of avoltage provided between the cathode and the anode, the electrons thusbeing concentrated on the anode to form a focus. The filaments arrangedin the focussing device are of different lengths. The long filament 1produces on the anode surface a band-shaped focal spot of a size largerthan that of the focal spot produced by means of the short filament 8.The two impact areas for the electrons preferably coincide.

The filaments are heated by a heating-current transformer B, of whichsecondary winding It] is connected, at one end, by way of a supply wireI l to the two filaments l and '8. The other end of the secondarywinding is connected to a movable arm 'l2 of a switch having twostationary contacts l3 and M, which are connected by way of supply wiresl5 and I6 respectively to the free extremity of the short filament 8 andthe free extremity of the long filament 9 respectively. The switch isshunted by a resistance it between the stationary contact i4 and themovable arm l2. During the screening operation, the arm I? of the switchengages the stationary contact 13, so that the short filament 8 isconnected to the transformer winding l0. As soon as the primary windingI8 of the transformer 9 is con nected to the mains, said filament isheated up to the tempera-ture at which electron emission takes place. Ittakes some time before this temperature is attained, but this is notobjectionable. However, this would be disadvantageous if, afterscreening, it would be necessary to wait for an equal time before aphotograph can be taken. Upon switching-in the heating-currenttransformer 9, a current already flows from the secondary winding H]through the long filament '1', said current being limited to adetermined value due to the presence of resistance I! in this circuit,the filament thus being heated but just not reaching the temperature atwhich electron emission takes place. By switching-over the movable arm12 of the switch from the stationary contact l3 to the other stationarycontact 14, resistance l! is short-circuited, the current flowingthrough the filament I increasing to a value at which the full amount ofX-rays is produced. Upon switching-over, the current flowing throughfilament 8 is interrupted.

The time in which the cathode for photographing attains the emissiontemperature after the screening operation is terminated may be veryshort, for example 0.8 sec. A particular circumstance in this circuit isthat the heating time of the cathode for photographing corresponds tothe time which normally elapses between screening and photographing andin which the preparations for taking the photograph are made.

The anode current is supplied to the X-ray tube from a high-tensiondevice i9 by way of supply wires 20.

In an X-ray device comprising the above-described circuit, use may bemade of the particular circumstance mentioned above for rendering thedevice automatic.

According to a further feature of the invention, for this purpose use ismade of an electromagnetic switch comprising a break-contact and amake-contact, which is operated by a hand switch and which is adapted tooccupy two positions, in one of which the X-ray tube is switched-in forscreening and in the other the photographing process is automaticallyinitiated and carried out. In Fig. 2, the electro-magnetic switch andthe hand switch are designated 21 and 22 respectively. The hand switch22 is operated when from screening has to be changed-over tophotographing. Of the two contacts 23 and 24 provided on the switch 2!,contact 23 is interrupted and contact 24 is closed when the hand switch22 is closed as a result of the magnet coil 25 being energised due tocurrent starting to fiow from a source of supply 26 through a conductor21, through the coil 25 and by way of the hand switch 22 through aconductor 28 back to the source of supply. When the contact 23 betweenthe points of contact 29 and 30 is opened, the energising currentflowing through a relay coil 3| is interrupted thus causing a switch 32to interrupt the supply of current to the primary winding 33 of ahigh-tension transformer 34. Then there is no longer any voltage set upbetween the anode 3 and the cathode of the X-r-ay tube I.

In this position of the electro-magnetic switch 2|, the circuits of tworelay coils 35 and 36 are connected to the source of supply 26. The coil35 operates an X-ray film cassette 37, shifting it to the positionrequired for photographing. The coil 36 causes a movable arm 52 of aswitch included in the common heating-current conductor, correspondingto the arm l2 of Fig. 1, to be switched-over from a stationary contact53 to a stationary contact 54, a resistance 51 thus beingshort-circuited. This results in the filament 8 being switched off andthe filament I having supplied to it the full current through thesecondary winding of a heating-current transformer 9'. The use of aheating-current transformer 9 and 9 respectively for each of the twofilaments 1 and 8 affords the advantage that the switching arm 52 isincluded in a circuit having a low potential with respect to earth. Inthis case it is not necessary to take special steps for insulating therelay coil 36 with respect to the switching arm.

When the cassette 3! has been moved into position, which is, forexample, 0.8 sec. later than the moment at which the hand switch wasoperated, the contacts 38 and 39 engage one another, thus closing thecircuit including the coil 3| and shunting the break-contact 23 ofswitch 2!. The circuit includes a time switch 40 which, after a presetduration, causes the energizing current for the coil 3i, which closedthe switch 32 in the supply mains to the primary winding of thehigh-tension transformer due to closure of the contacts 38 and 39 to beinterrupted and thus the photographing process to be terminated.

The primary windings of the heating-current transformer 9, 9" and of thehigh-tension transformer 32 are connected by way of a main switch 4i tothe mains.

What I claim is:

1. The combination of an X-ray tube having an anode and a pair oifilaments and a circuit arrangement for energizing the same, comprisinga source of heating current, means coupling one terminal of said currentsource to both of said filaments, a resistor connected between the otherterminal of said source and one of said filaments, switching meansconnected between said other terminal of said source and the otherfilament and adapted to close the circuit to said other filament in oneposition and to open that circuit and short out the resistor in anotherposition, a first relay having a normally-closed contact and a normallyopen contact, means for applying a high potential. between said anodeand said filaments of said X-ray tube, a movable cassette adapted toreceive a photographic film, a source of potential, a second relayhaving a winding in series with said normally-closed switch and saidpotential source and contacts adapted to energize and deenergize thehigh potential means, a third relay having a winding in series with saidnormally open contact and said potential source and adapted to actuatesaid switching means from said one position to said other position, afourth relay having a winding in series with said normally-open contactand said potential source and coupled to said cassette such that uponenergization the cassette is moved to a position to receive X-raysemanating from the anode, and manual means for energizing the firstrelay to thereby initiate an automatic process for taking a radiograph.

2. The combination of an X-ray tube having an anode and a pair offilaments and a circuit arrangement for energizing the same, comprisinga source of heating current, means coupling one terminal of said currentsource to both of said filaments, a resistor connected between the otherterminal of said source and one of said filaments, switching meansconnected between said other terminal of said source and the otherfilament and adapted to close the circuit to said other filament in oneposition and to open that circuit and short out the resistor in anotherposition, a first relay having a normally-closed contact and anormally-open contact, means for applying a high potential between saidanode and said filaments of said X-ray tube, a movable cassette adaptedto receive a photographic film, a source of potential, a second relayhaving a winding in series with said normally-closed switch and saidpotential source and contacts adapted to energize and deenergize thehigh potential means, a third relay having a winding in series with saidnormally-open contact and said potential source and adapted to actuatesaid switching means from said one position to said other position,'afourth relay having a winding in series with said normally-open contactand said potential source and coupled to said cassette such that uponenergization the cassette is moved to a position to receive X-raysemanating from the anode, a contact device responsive to movement ofsaid cassette and adapted to short out said normally-closed contact whensaid cassette is moved into the position toreceive X-rays and therebyconnect the high potential means to said tube, timing means connected inseries with said contact device for determining the duration of theapplication of said high potential to said tube, and manual means forenergizing the first relay to thereby initiate an automatic process fortaking a radiograph.

3. The combination of an X-ray tube having an anode and a pair offilaments and a circuit arrangement for energizing the same, comprisinga source of heating current, means coupling one terminal of said currentsource to both of said filaments, a resistor connected between the otherterminal of said source and one of said filaments, switching meansconnected between said other terminal of said source and the otherfilament and, adapted to close the circuit to said other filament in oneposition and to open that circuit and short out the resistor in anotherposition, a first relay having a normally-closed contact and anormally-open contact, means for applying a high potential between saidanode and said filaments of said X-ray tube, a movable cassette adaptedto receive a photographic film, means responsive to energization of saidrelay to successively move said cassette to a position to receive X-raysemanating from the anode, actuate said switching means from said oneposition to said other position and apply the high potential betweensaid anode and said filaments, and means for energizing said first relayto thereby initiate an automatic process for taking a radiograph.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,907,508 Coolidge May 9, 1933 2,132,537 McCurdy Oct. 11, 19382,146,900 Klinckmann Feb. 14, 1939 2,160,605 Suits May 30, 1939

